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解构赋值</span></h1> <div class="re-page-index"><div class="page-index-title"><span class="open-catalog"><svg aria-hidden="true" class="icon arrow-right"><use xlink:href="#icon-bold-right"></use></svg> <span class="text">目录</span></span></div> <div class="page-index-content"><div class="page-catalog" style="display:none;"><div class="synopsis-wrap"><ul class="synopsis-ul"><li class="synopsis-li"><a href="/docs/js/es6/anatomy-assignment.html#默认参数" class="synopsis-link">默认参数</a></li><li class="synopsis-li"><a href="/docs/js/es6/anatomy-assignment.html#剩余参数" class="synopsis-link">剩余参数</a></li><li class="synopsis-li"><a href="/docs/js/es6/anatomy-assignment.html#数组解构赋值" class="synopsis-link">数组解构赋值</a></li><li class="synopsis-li"><a href="/docs/js/es6/anatomy-assignment.html#对象解构赋值" class="synopsis-link">对象解构赋值</a></li><li class="synopsis-li"><a href="/docs/js/es6/anatomy-assignment.html#设置函数默认值" class="synopsis-link">设置函数默认值</a></li><li class="synopsis-li"><a href="/docs/js/es6/anatomy-assignment.html#对象浅拷贝" class="synopsis-link">对象浅拷贝</a></li><li class="synopsis-li"><a href="/docs/js/es6/anatomy-assignment.html#对象属性加强" class="synopsis-link">对象属性加强</a></li></ul></div></div></div></div></div> <div class="theme-default-content content__default"><h2 id="默认参数"><a href="#默认参数" class="header-anchor">#</a> 默认参数</h2> <p>在 ES5 之前，只能通过 <code>||</code> 来设置默认参数。</p> <div class="language-js extra-class"><pre class="language-js"><code><span class="token keyword">function</span> <span class="token function">sum</span><span class="token punctuation">(</span><span class="token parameter">a<span class="token punctuation">,</span> b</span><span class="token punctuation">)</span><span class="token punctuation">{</span>
  a <span class="token operator">=</span> a <span class="token operator">||</span> <span class="token number">0</span>
  b <span class="token operator">=</span> b <span class="token operator">||</span> <span class="token number">0</span>
  <span class="token keyword">return</span> a <span class="token operator">+</span> b
<span class="token punctuation">}</span>
</code></pre></div><p><strong>ES6<sup>+</sup></strong> 中可以直接使用 <code>=</code> 来设置：</p> <div class="language-js extra-class"><pre class="language-js"><code><span class="token keyword">function</span> <span class="token function">sum</span><span class="token punctuation">(</span><span class="token parameter">a <span class="token operator">=</span> <span class="token number">0</span><span class="token punctuation">,</span> b <span class="token operator">=</span> <span class="token number">0</span></span><span class="token punctuation">)</span><span class="token punctuation">{</span>
  <span class="token keyword">return</span> a <span class="token operator">+</span> b
<span class="token punctuation">}</span>
</code></pre></div><h2 id="剩余参数"><a href="#剩余参数" class="header-anchor">#</a> 剩余参数</h2> <p>如果要给一个函数传入多个不确定个数的参数，<strong>ES5</strong> 只能通过循环 <code>arguments</code> 获取：</p> <div class="language-js extra-class"><pre class="language-js"><code><span class="token keyword">function</span> <span class="token function">sum</span><span class="token punctuation">(</span><span class="token parameter">message</span><span class="token punctuation">)</span><span class="token punctuation">{</span>
    <span class="token keyword">var</span> result <span class="token operator">=</span> <span class="token number">0</span>
    <span class="token keyword">for</span><span class="token punctuation">(</span><span class="token keyword">var</span> i <span class="token operator">=</span> <span class="token number">1</span><span class="token punctuation">;</span> i <span class="token operator">&lt;</span> arguments<span class="token punctuation">.</span>length<span class="token punctuation">;</span> i<span class="token operator">++</span><span class="token punctuation">)</span><span class="token punctuation">{</span>
        result <span class="token operator">+=</span> arguments<span class="token punctuation">[</span>i<span class="token punctuation">]</span>
    <span class="token punctuation">}</span>
    <span class="token keyword">return</span> message <span class="token operator">+</span> result
<span class="token punctuation">}</span>
<span class="token function">sum</span><span class="token punctuation">(</span><span class="token string">'结果是：'</span><span class="token punctuation">,</span> <span class="token number">1</span><span class="token punctuation">,</span> <span class="token number">2</span><span class="token punctuation">,</span> <span class="token number">3</span><span class="token punctuation">,</span> <span class="token number">4</span><span class="token punctuation">)</span> <span class="token comment">// 输出：&quot;结果是：10&quot;</span>
</code></pre></div><p><strong>ES6<sup>+</sup></strong> 新增了 <code>...</code> 的写法：</p> <div class="language-js extra-class"><pre class="language-js"><code><span class="token keyword">function</span> <span class="token function">sum</span><span class="token punctuation">(</span><span class="token parameter">message<span class="token punctuation">,</span> <span class="token operator">...</span>numbers</span><span class="token punctuation">)</span><span class="token punctuation">{</span>
    <span class="token keyword">let</span> result <span class="token operator">=</span> <span class="token number">0</span>
    <span class="token keyword">for</span><span class="token punctuation">(</span><span class="token keyword">let</span> i<span class="token operator">=</span><span class="token number">0</span><span class="token punctuation">;</span> i<span class="token operator">&lt;</span>numbers<span class="token punctuation">.</span>length<span class="token punctuation">;</span> i<span class="token operator">++</span><span class="token punctuation">)</span><span class="token punctuation">{</span>
        result <span class="token operator">+=</span> numbers<span class="token punctuation">[</span>i<span class="token punctuation">]</span>
    <span class="token punctuation">}</span>
    <span class="token keyword">return</span> message <span class="token operator">+</span> result
<span class="token punctuation">}</span>
<span class="token function">sum</span><span class="token punctuation">(</span><span class="token string">'结果是：'</span><span class="token punctuation">,</span> <span class="token number">1</span><span class="token punctuation">,</span> <span class="token number">2</span><span class="token punctuation">,</span> <span class="token number">3</span><span class="token punctuation">,</span> <span class="token number">4</span><span class="token punctuation">)</span> <span class="token comment">// 输出：&quot;结果是：10&quot;</span>
</code></pre></div><p>上面的代码还可以使用 <code>.reduce()</code> 来简化循环的步骤。</p> <div class="language-js extra-class"><pre class="language-js"><code><span class="token keyword">function</span> <span class="token function">sum</span><span class="token punctuation">(</span><span class="token parameter">message<span class="token punctuation">,</span> <span class="token operator">...</span>numbers</span><span class="token punctuation">)</span><span class="token punctuation">{</span>
    <span class="token keyword">let</span> result <span class="token operator">=</span> numbers<span class="token punctuation">.</span><span class="token function">reduce</span><span class="token punctuation">(</span><span class="token punctuation">(</span><span class="token parameter">p<span class="token punctuation">,</span> v</span><span class="token punctuation">)</span><span class="token operator">=&gt;</span>p<span class="token operator">+</span>v<span class="token punctuation">,</span> <span class="token number">0</span><span class="token punctuation">)</span>
    <span class="token keyword">return</span> message <span class="token operator">+</span> result
<span class="token punctuation">}</span>
<span class="token function">sum</span><span class="token punctuation">(</span><span class="token string">'结果是：'</span><span class="token punctuation">,</span> <span class="token number">1</span><span class="token punctuation">,</span> <span class="token number">2</span><span class="token punctuation">,</span> <span class="token number">3</span><span class="token punctuation">,</span> <span class="token number">4</span><span class="token punctuation">)</span> <span class="token comment">// 输出：&quot;结果是：10&quot;</span>
</code></pre></div><p>并且 <code>...</code> 也支持数组及及对象的合并，如下：</p> <div class="language-js extra-class"><pre class="language-js"><code><span class="token keyword">let</span> array1 <span class="token operator">=</span> <span class="token punctuation">[</span><span class="token number">1</span><span class="token punctuation">,</span> <span class="token number">2</span><span class="token punctuation">,</span> <span class="token number">3</span><span class="token punctuation">,</span> <span class="token number">4</span><span class="token punctuation">,</span> <span class="token number">5</span><span class="token punctuation">,</span> <span class="token number">6</span><span class="token punctuation">]</span>
<span class="token keyword">let</span> array2 <span class="token operator">=</span> <span class="token punctuation">[</span><span class="token number">0</span><span class="token punctuation">,</span> <span class="token operator">...</span>array1<span class="token punctuation">,</span> <span class="token number">7</span><span class="token punctuation">]</span>
</code></pre></div><p>而在 ES5 之前，要完成上面的操作需要更复杂的方式：</p> <div class="language-js extra-class"><pre class="language-js"><code><span class="token keyword">let</span> array1 <span class="token operator">=</span> <span class="token punctuation">[</span><span class="token number">1</span><span class="token punctuation">,</span> <span class="token number">2</span><span class="token punctuation">,</span> <span class="token number">3</span><span class="token punctuation">,</span> <span class="token number">4</span><span class="token punctuation">,</span> <span class="token number">5</span><span class="token punctuation">,</span> <span class="token number">6</span><span class="token punctuation">]</span>
<span class="token keyword">let</span> array2 <span class="token operator">=</span> <span class="token punctuation">[</span><span class="token number">0</span><span class="token punctuation">]</span><span class="token punctuation">.</span><span class="token function">concat</span><span class="token punctuation">(</span>array1<span class="token punctuation">)</span><span class="token punctuation">.</span><span class="token function">concat</span><span class="token punctuation">(</span><span class="token punctuation">[</span><span class="token number">7</span><span class="token punctuation">]</span><span class="token punctuation">)</span>
</code></pre></div><h2 id="数组解构赋值"><a href="#数组解构赋值" class="header-anchor">#</a> 数组解构赋值</h2> <p><strong>ES6<sup>+</sup></strong> 新增了通过数组来赋值转换的功能</p> <div class="language-js extra-class"><pre class="language-js"><code><span class="token keyword">let</span> a <span class="token operator">=</span> <span class="token number">1</span>
<span class="token keyword">let</span> b <span class="token operator">=</span> <span class="token number">2</span>
<span class="token punctuation">;</span><span class="token punctuation">[</span>a<span class="token punctuation">,</span> b<span class="token punctuation">]</span> <span class="token operator">=</span> <span class="token punctuation">[</span>b<span class="token punctuation">,</span> a<span class="token punctuation">]</span> <span class="token comment">// 此处要加分号，否则这行代码会向上变为一行</span>
console<span class="token punctuation">.</span><span class="token function">log</span><span class="token punctuation">(</span><span class="token string">'a: '</span> <span class="token operator">+</span> a <span class="token string">'，b: '</span> <span class="token operator">+</span> b<span class="token punctuation">)</span> <span class="token comment">// a: 2，b: 1</span>
</code></pre></div><p>还可以结合 <code>...</code> 来批量赋值</p> <div class="language-js extra-class"><pre class="language-js"><code><span class="token keyword">let</span> <span class="token punctuation">[</span>a<span class="token punctuation">,</span> b<span class="token punctuation">,</span> <span class="token operator">...</span>rest<span class="token punctuation">]</span> <span class="token operator">=</span> <span class="token punctuation">[</span><span class="token number">10</span><span class="token punctuation">,</span> <span class="token number">20</span><span class="token punctuation">,</span> <span class="token number">30</span><span class="token punctuation">,</span> <span class="token number">40</span><span class="token punctuation">,</span> <span class="token number">50</span><span class="token punctuation">]</span>
console<span class="token punctuation">.</span><span class="token function">log</span><span class="token punctuation">(</span>rest<span class="token punctuation">)</span> <span class="token comment">// [30, 40, 50]</span>
</code></pre></div><div class="custom-block tip"><p class="custom-block-title">注意</p> <p>此处不能在 <code>...rest</code> 后再追加变量，剩余参数只能放在最后，否则会出现语法歧义。</p></div> <p>还可以使用函数返回一个对象</p> <div class="language-js extra-class"><pre class="language-js"><code><span class="token keyword">function</span> <span class="token function">fn</span><span class="token punctuation">(</span><span class="token punctuation">)</span><span class="token punctuation">{</span>
  <span class="token keyword">return</span> <span class="token punctuation">[</span><span class="token number">1</span><span class="token punctuation">,</span> <span class="token number">2</span><span class="token punctuation">]</span>
<span class="token punctuation">}</span>
<span class="token keyword">let</span> <span class="token punctuation">[</span>a<span class="token punctuation">,</span> b<span class="token punctuation">]</span> <span class="token operator">=</span> <span class="token function">fn</span><span class="token punctuation">(</span><span class="token punctuation">)</span>
</code></pre></div><p>并且在赋值时还支持设置默认值</p> <div class="language-js extra-class"><pre class="language-js"><code><span class="token keyword">let</span> <span class="token punctuation">[</span>a <span class="token operator">=</span> <span class="token number">5</span><span class="token punctuation">,</span> b <span class="token operator">=</span> <span class="token number">7</span><span class="token punctuation">]</span> <span class="token operator">=</span> <span class="token punctuation">[</span><span class="token number">1</span><span class="token punctuation">]</span>
console<span class="token punctuation">.</span><span class="token function">log</span><span class="token punctuation">(</span>a<span class="token punctuation">,</span> b<span class="token punctuation">)</span> <span class="token comment">// 1 7</span>
</code></pre></div><h2 id="对象解构赋值"><a href="#对象解构赋值" class="header-anchor">#</a> 对象解构赋值</h2> <p>在 ES5 之前，对象批量赋值只能通过以下方式</p> <div class="language-js extra-class"><pre class="language-js"><code><span class="token keyword">let</span> sun <span class="token operator">=</span> <span class="token punctuation">{</span>name<span class="token operator">:</span> <span class="token string">'isSun'</span><span class="token punctuation">,</span> age<span class="token operator">:</span> <span class="token number">18</span><span class="token punctuation">,</span> gender<span class="token operator">:</span> <span class="token string">'Male'</span><span class="token punctuation">}</span>
<span class="token keyword">let</span> name <span class="token operator">=</span> sun<span class="token punctuation">.</span>name
<span class="token keyword">let</span> age <span class="token operator">=</span> sun<span class="token punctuation">.</span>age
<span class="token keyword">let</span> gender <span class="token operator">=</span> sun<span class="token punctuation">.</span>gender
</code></pre></div><p>而 <strong>ES6<sup>+</sup></strong> 的新语法添加了通过对象来批量赋值</p> <div class="language-js extra-class"><pre class="language-js"><code><span class="token keyword">let</span> sun <span class="token operator">=</span> <span class="token punctuation">{</span>name<span class="token operator">:</span> <span class="token string">'isSun'</span><span class="token punctuation">,</span> age<span class="token operator">:</span> <span class="token number">18</span><span class="token punctuation">,</span> gender<span class="token operator">:</span> <span class="token string">'Male'</span><span class="token punctuation">}</span>
<span class="token keyword">let</span> <span class="token punctuation">{</span>name<span class="token punctuation">,</span> age<span class="token punctuation">,</span> gender<span class="token punctuation">}</span> <span class="token operator">=</span> sun
</code></pre></div><p>赋值时还可通过修改对象的属性名来修改变量名</p> <div class="language-js extra-class"><pre class="language-js"><code><span class="token keyword">let</span> sun <span class="token operator">=</span> <span class="token punctuation">{</span>
  name<span class="token operator">:</span> <span class="token string">'Jack'</span><span class="token punctuation">,</span> age<span class="token operator">:</span> <span class="token number">18</span><span class="token punctuation">,</span> gender<span class="token operator">:</span> <span class="token string">'Male'</span>
<span class="token punctuation">}</span>
<span class="token keyword">let</span> <span class="token punctuation">{</span>name<span class="token operator">:</span> serial<span class="token punctuation">}</span> <span class="token operator">=</span> sun
console<span class="token punctuation">.</span><span class="token function">log</span><span class="token punctuation">(</span>serial<span class="token punctuation">)</span> <span class="token comment">// 输出：Jack</span>
</code></pre></div><p>该方法还支持嵌套，如修改子对象的属性名</p> <div class="language-js extra-class"><pre class="language-js"><code><span class="token keyword">let</span> sun <span class="token operator">=</span> <span class="token punctuation">{</span>
  name<span class="token operator">:</span> <span class="token string">'Jack'</span><span class="token punctuation">,</span>
  age<span class="token operator">:</span> <span class="token number">18</span><span class="token punctuation">,</span>
  gender<span class="token operator">:</span> <span class="token string">'Male'</span><span class="token punctuation">,</span>
  child<span class="token operator">:</span> <span class="token punctuation">{</span>
    name<span class="token operator">:</span> <span class="token string">'Tom'</span><span class="token punctuation">,</span> age<span class="token operator">:</span> <span class="token number">6</span><span class="token punctuation">,</span> gender<span class="token operator">:</span> <span class="token string">'Male'</span>
  <span class="token punctuation">}</span>
<span class="token punctuation">}</span>
<span class="token keyword">let</span> <span class="token punctuation">{</span>child<span class="token operator">:</span> <span class="token punctuation">{</span>name<span class="token operator">:</span> serial<span class="token punctuation">}</span><span class="token punctuation">}</span> <span class="token operator">=</span> sun
console<span class="token punctuation">.</span><span class="token function">log</span><span class="token punctuation">(</span>serial<span class="token punctuation">)</span> <span class="token comment">// 输出：Tom</span>
</code></pre></div><p>并且子对象赋值时也可添加默认参数（如果子对象没有该属性，则使用默认参数），同时子对象的属性也可以使用批量声明。</p> <div class="language-js extra-class"><pre class="language-js"><code><span class="token keyword">let</span> sun <span class="token operator">=</span> <span class="token punctuation">{</span>
  name<span class="token operator">:</span> <span class="token string">'Jack'</span><span class="token punctuation">,</span>
  age<span class="token operator">:</span> <span class="token number">18</span><span class="token punctuation">,</span>
  gender<span class="token operator">:</span> <span class="token string">'Male'</span><span class="token punctuation">,</span>
  child<span class="token operator">:</span> <span class="token punctuation">{</span>
    name<span class="token operator">:</span> <span class="token string">'Jerry'</span><span class="token punctuation">,</span> age<span class="token operator">:</span> <span class="token number">6</span><span class="token punctuation">,</span> gender<span class="token operator">:</span> <span class="token string">'Male'</span>
  <span class="token punctuation">}</span>
<span class="token punctuation">}</span>
<span class="token keyword">let</span> <span class="token punctuation">{</span> child<span class="token operator">:</span> <span class="token punctuation">{</span> name<span class="token operator">:</span> serial<span class="token operator">=</span><span class="token string">'Tom'</span><span class="token punctuation">,</span> age<span class="token punctuation">,</span> gender <span class="token punctuation">}</span> <span class="token punctuation">}</span> <span class="token operator">=</span> sun
console<span class="token punctuation">.</span><span class="token function">log</span><span class="token punctuation">(</span>serial<span class="token punctuation">)</span> <span class="token comment">// 输出：Jerry</span>
console<span class="token punctuation">.</span><span class="token function">log</span><span class="token punctuation">(</span>age<span class="token punctuation">,</span> gender<span class="token punctuation">)</span> <span class="token comment">// 输出：6 &quot;Male&quot;</span>
</code></pre></div><p>也可以根据同名 key 解构赋值</p> <div class="language-typescript extra-class"><pre class="language-typescript"><code><span class="token punctuation">(</span><span class="token punctuation">{</span> a<span class="token punctuation">,</span> b <span class="token punctuation">}</span> <span class="token operator">=</span> <span class="token punctuation">{</span> a<span class="token operator">:</span> <span class="token string">&quot;baz&quot;</span><span class="token punctuation">,</span> b<span class="token operator">:</span> <span class="token number">101</span> <span class="token punctuation">}</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
</code></pre></div><blockquote><p>注意，我们需要用括号将它括起来，因为Javascript通常会将以 <code>{</code> 起始的语句解析为一个块。</p></blockquote> <h2 id="设置函数默认值"><a href="#设置函数默认值" class="header-anchor">#</a> 设置函数默认值</h2> <p>在 ES5 之前，设置函数默认值要经过一系列的判断</p> <div class="language-js extra-class"><pre class="language-js"><code><span class="token keyword">function</span> <span class="token function">fn</span><span class="token punctuation">(</span><span class="token parameter">options</span><span class="token punctuation">)</span> <span class="token punctuation">{</span>
  options <span class="token operator">=</span> options <span class="token operator">===</span> <span class="token keyword">undefined</span> <span class="token operator">?</span> <span class="token punctuation">{</span><span class="token punctuation">}</span> <span class="token operator">:</span> options<span class="token punctuation">;</span>
  <span class="token keyword">var</span> size <span class="token operator">=</span> options<span class="token punctuation">.</span>size <span class="token operator">===</span> <span class="token keyword">undefined</span> <span class="token operator">?</span> <span class="token string">'big'</span> <span class="token operator">:</span> options<span class="token punctuation">.</span>size<span class="token punctuation">;</span>
  <span class="token keyword">var</span> cords <span class="token operator">=</span> options<span class="token punctuation">.</span>cords <span class="token operator">===</span> <span class="token keyword">undefined</span> <span class="token operator">?</span> <span class="token punctuation">{</span> x<span class="token operator">:</span> <span class="token number">0</span><span class="token punctuation">,</span> y<span class="token operator">:</span> <span class="token number">0</span> <span class="token punctuation">}</span> <span class="token operator">:</span> options<span class="token punctuation">.</span>cords<span class="token punctuation">;</span>
  <span class="token keyword">var</span> radius <span class="token operator">=</span> options<span class="token punctuation">.</span>radius <span class="token operator">===</span> <span class="token keyword">undefined</span> <span class="token operator">?</span> <span class="token number">25</span> <span class="token operator">:</span> options<span class="token punctuation">.</span>radius<span class="token punctuation">;</span>
  console<span class="token punctuation">.</span><span class="token function">log</span><span class="token punctuation">(</span>size<span class="token punctuation">,</span> cords<span class="token punctuation">,</span> radius<span class="token punctuation">)</span><span class="token punctuation">;</span>
  <span class="token comment">// now finally do some chart drawing</span>
<span class="token punctuation">}</span>

<span class="token function">fn</span><span class="token punctuation">(</span><span class="token punctuation">{</span>
  cords<span class="token operator">:</span> <span class="token punctuation">{</span> x<span class="token operator">:</span> <span class="token number">18</span><span class="token punctuation">,</span> y<span class="token operator">:</span> <span class="token number">30</span> <span class="token punctuation">}</span><span class="token punctuation">,</span>
  radius<span class="token operator">:</span> <span class="token number">30</span>
<span class="token punctuation">}</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
</code></pre></div><p><strong>ES6<sup>+</sup></strong> 新语法将上面的写法简化为对象形式</p> <div class="language-js extra-class"><pre class="language-js"><code><span class="token keyword">function</span> <span class="token function">fn</span><span class="token punctuation">(</span><span class="token punctuation">{</span>size <span class="token operator">=</span> <span class="token string">'big'</span><span class="token punctuation">,</span> cords <span class="token operator">=</span> <span class="token punctuation">{</span> x<span class="token operator">:</span> <span class="token number">0</span><span class="token punctuation">,</span> y<span class="token operator">:</span> <span class="token number">0</span> <span class="token punctuation">}</span><span class="token punctuation">,</span> radius <span class="token operator">=</span> <span class="token number">25</span><span class="token punctuation">}</span> <span class="token operator">=</span> <span class="token punctuation">{</span><span class="token punctuation">}</span><span class="token punctuation">)</span> <span class="token punctuation">{</span>
  console<span class="token punctuation">.</span><span class="token function">log</span><span class="token punctuation">(</span>size<span class="token punctuation">,</span> cords<span class="token punctuation">,</span> radius<span class="token punctuation">)</span><span class="token punctuation">;</span>
<span class="token punctuation">}</span>
<span class="token function">fn</span><span class="token punctuation">(</span><span class="token punctuation">{</span>
  cords<span class="token operator">:</span> <span class="token punctuation">{</span> x<span class="token operator">:</span> <span class="token number">18</span><span class="token punctuation">,</span> y<span class="token operator">:</span> <span class="token number">30</span> <span class="token punctuation">}</span><span class="token punctuation">,</span>
  radius<span class="token operator">:</span> <span class="token number">30</span>
<span class="token punctuation">}</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
</code></pre></div><p>如果觉得复杂，还可以这么写</p> <div class="language-js extra-class"><pre class="language-js"><code><span class="token keyword">function</span> <span class="token function">fn</span><span class="token punctuation">(</span><span class="token parameter">options <span class="token operator">=</span> <span class="token punctuation">{</span><span class="token punctuation">}</span></span><span class="token punctuation">)</span> <span class="token punctuation">{</span>
  <span class="token keyword">let</span> <span class="token punctuation">{</span>size <span class="token operator">=</span> <span class="token string">'big'</span><span class="token punctuation">,</span> cords <span class="token operator">=</span> <span class="token punctuation">{</span> x<span class="token operator">:</span> <span class="token number">0</span><span class="token punctuation">,</span> y<span class="token operator">:</span> <span class="token number">0</span> <span class="token punctuation">}</span><span class="token punctuation">,</span> radius <span class="token operator">=</span> <span class="token number">25</span><span class="token punctuation">}</span> <span class="token operator">=</span> options
  console<span class="token punctuation">.</span><span class="token function">log</span><span class="token punctuation">(</span>size<span class="token punctuation">,</span> cords<span class="token punctuation">,</span> radius<span class="token punctuation">)</span><span class="token punctuation">;</span>
<span class="token punctuation">}</span>

<span class="token function">fn</span><span class="token punctuation">(</span><span class="token punctuation">{</span>
  cords<span class="token operator">:</span> <span class="token punctuation">{</span> x<span class="token operator">:</span> <span class="token number">18</span><span class="token punctuation">,</span> y<span class="token operator">:</span> <span class="token number">30</span> <span class="token punctuation">}</span><span class="token punctuation">,</span>
  radius<span class="token operator">:</span> <span class="token number">30</span>
<span class="token punctuation">}</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
</code></pre></div><p>参考MDN文档：<a href="https://developer.mozilla.org/zh-CN/docs/Web/JavaScript/Reference/Operators/Destructuring_assignment#%E5%87%BD%E6%95%B0%E5%8F%82%E6%95%B0%E9%BB%98%E8%AE%A4%E5%80%BC" target="_blank" rel="noopener noreferrer">函数参数默认值<span><svg xmlns="http://www.w3.org/2000/svg" aria-hidden="true" focusable="false" x="0px" y="0px" viewBox="0 0 100 100" width="15" height="15" class="icon outbound"><path fill="currentColor" d="M18.8,85.1h56l0,0c2.2,0,4-1.8,4-4v-32h-8v28h-48v-48h28v-8h-32l0,0c-2.2,0-4,1.8-4,4v56C14.8,83.3,16.6,85.1,18.8,85.1z"></path> <polygon fill="currentColor" points="45.7,48.7 51.3,54.3 77.2,28.5 77.2,37.2 85.2,37.2 85.2,14.9 62.8,14.9 62.8,22.9 71.5,22.9"></polygon></svg> <span class="sr-only">(opens new window)</span></span></a></p> <h2 id="对象浅拷贝"><a href="#对象浅拷贝" class="header-anchor">#</a> 对象浅拷贝</h2> <p>浅拷贝通常指的是只会拷贝对象的第一层属性。使用 <strong>ES6<sup>+</sup></strong> 的两种语法都可以实现简单的浅拷贝</p> <div class="language-js extra-class"><pre class="language-js"><code><span class="token keyword">let</span> objA <span class="token operator">=</span> <span class="token punctuation">{</span>
    name<span class="token operator">:</span> <span class="token punctuation">{</span>
        x<span class="token operator">:</span> <span class="token string">'a'</span>
    <span class="token punctuation">}</span>
<span class="token punctuation">}</span>

<span class="token keyword">let</span> objB <span class="token operator">=</span> Object<span class="token punctuation">.</span><span class="token function">assign</span><span class="token punctuation">(</span><span class="token punctuation">{</span><span class="token punctuation">}</span><span class="token punctuation">,</span> objA<span class="token punctuation">)</span>
console<span class="token punctuation">.</span><span class="token function">log</span><span class="token punctuation">(</span>objB<span class="token punctuation">)</span> <span class="token comment">// {name: {x: &quot;b&quot;}}</span>

<span class="token keyword">let</span> objC <span class="token operator">=</span> <span class="token punctuation">{</span><span class="token operator">...</span>objA<span class="token punctuation">}</span>
console<span class="token punctuation">.</span><span class="token function">log</span><span class="token punctuation">(</span>objC<span class="token punctuation">)</span> <span class="token comment">// {name: {x: &quot;b&quot;}}</span>
</code></pre></div><p>上面两种语法还可以用来合并对象</p> <p><strong>ES6<sup>+</sup></strong> 新增了两种方式合并来合并一个对象</p> <p>使用 <code>Object.assign()</code> 合并对象</p> <div class="language-js extra-class"><pre class="language-js"><code><span class="token keyword">let</span> objA <span class="token operator">=</span> <span class="token punctuation">{</span>
    p1<span class="token operator">:</span> <span class="token number">1</span><span class="token punctuation">,</span>
    p2<span class="token operator">:</span> <span class="token number">2</span>
<span class="token punctuation">}</span>
<span class="token keyword">let</span> objB <span class="token operator">=</span> <span class="token punctuation">{</span>
    p1<span class="token operator">:</span> <span class="token number">1250</span><span class="token punctuation">,</span>
    p3<span class="token operator">:</span> <span class="token number">3</span>
<span class="token punctuation">}</span>

<span class="token keyword">let</span> objC <span class="token operator">=</span> Object<span class="token punctuation">.</span><span class="token function">assign</span><span class="token punctuation">(</span><span class="token punctuation">{</span><span class="token punctuation">}</span><span class="token punctuation">,</span> objA<span class="token punctuation">,</span> objB<span class="token punctuation">)</span>
console<span class="token punctuation">.</span><span class="token function">log</span><span class="token punctuation">(</span>objC<span class="token punctuation">)</span> <span class="token comment">// 输出：{p1: 1250, p2: 2, p3: 3}</span>

<span class="token keyword">let</span> objD <span class="token operator">=</span> <span class="token punctuation">{</span><span class="token operator">...</span>objA<span class="token punctuation">,</span> <span class="token operator">...</span>objB<span class="token punctuation">}</span>
console<span class="token punctuation">.</span><span class="token function">log</span><span class="token punctuation">(</span>objD<span class="token punctuation">)</span> <span class="token comment">// 输出：{p1: 1250, p2: 2, p3: 3}</span>
</code></pre></div><h2 id="对象属性加强"><a href="#对象属性加强" class="header-anchor">#</a> 对象属性加强</h2> <p><strong>ES6<sup>+</sup></strong> 把变量赋值给对象的属性的语法简化了</p> <div class="language-js extra-class"><pre class="language-js"><code><span class="token keyword">let</span> x <span class="token operator">=</span> <span class="token number">1</span>
<span class="token keyword">let</span> y <span class="token operator">=</span> <span class="token number">2</span>
<span class="token keyword">let</span> obj <span class="token operator">=</span> <span class="token punctuation">{</span>x<span class="token punctuation">,</span> y<span class="token punctuation">}</span> <span class="token comment">// 等同于 let obj = {x: x, y: y}</span>
console<span class="token punctuation">.</span><span class="token function">log</span><span class="token punctuation">(</span>obj<span class="token punctuation">)</span> <span class="token comment">// {x: 1, y: 2}</span>
</code></pre></div><p>并且支持对象的 key 在赋值时传入变量（ES5之前只能通过 <code>object[xxx]</code> 的方式传入变量）</p> <div class="language-js extra-class"><pre class="language-js"><code><span class="token keyword">let</span> key <span class="token operator">=</span> <span class="token string">'x'</span>
<span class="token keyword">let</span> value <span class="token operator">=</span> <span class="token string">'y'</span>
<span class="token keyword">let</span> object <span class="token operator">=</span> <span class="token punctuation">{</span>
  <span class="token punctuation">[</span>key<span class="token punctuation">]</span><span class="token operator">:</span> value
<span class="token punctuation">}</span>
console<span class="token punctuation">.</span><span class="token function">log</span><span class="token punctuation">(</span>object<span class="token punctuation">)</span> <span class="token comment">// {x: &quot;y&quot;}</span>
</code></pre></div><p>中括号 (<code>[]</code>) 里还可以做简单的运算</p> <div class="language-js extra-class"><pre class="language-js"><code><span class="token keyword">let</span> key <span class="token operator">=</span> <span class="token string">'x'</span>
<span class="token keyword">let</span> value <span class="token operator">=</span> <span class="token string">'y'</span>
<span class="token keyword">let</span> obj <span class="token operator">=</span> <span class="token punctuation">{</span>
    <span class="token punctuation">[</span>key <span class="token operator">+</span> key<span class="token punctuation">]</span><span class="token operator">:</span> value
<span class="token punctuation">}</span>

console<span class="token punctuation">.</span><span class="token function">log</span><span class="token punctuation">(</span>obj<span class="token punctuation">)</span> <span class="token comment">// {xx: &quot;y&quot;}</span>
</code></pre></div></div> <footer class="page-edit"><!----> <div class="last-updated"><span class="prefix">上次更新：</span><span class="time">2021-05-05 16:41</span></div></footer> <div class="page-nav"><p class="inner"><span class="prev"><svg aria-hidden="true" class="icon"><use xlink:href="#icon-left"></use></svg> <a href="/docs/js/es6/new-object.html" class="prev">新版对象</a></span> <span class="next"><a href="/docs/js/es6/new-string.html">新版字符串</a> <svg aria-hidden="true" class="icon"><use xlink:href="#icon-right"></use></svg></span></p></div> </main></div><div class="global-ui"><!----><!----></div></div>
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